Systems for controlling the position of a geographic surface altering implement have been utilized for decades. For example, such control systems are used to move implements used on machinery such as bulldozers, motor graders, wheel loaders, compactors, pavers, asphalt layers, profilers, and the like. Typically, the control system enables a vehicle operator, depending upon the specific type of implement being controlled, to control lifting, tilting, and tipping of the implement by way of a fluid operated system. Because such systems are manually controlled (requires good hand-eye coordination) the accuracy and consistency of implement positioning will vary from operator to operator and from time to time. Since a substantial amount of trial and error is required by even the most skilled operator both efficiency and accuracy of operation will suffer.
To tilt an implement, for example the blade of a bulldozer, to an angle required to obtain the desired slope of cut is difficult for even the most skilled operator. This is based on the fact that the tilted angle of the blade is an operator observed position and not based on a fixed reference. It is particularly difficult to position and maintain the blade at a desired resultant angle under the dynamics of vehicle operation since any visual reference made to the terrain varies as the machine travels along the underlying surface. Thus, numerous additional passes of the dozing vehicle and frequent checks (surveys) of the worked surface are required.
Attempts have been made to automate positioning of geographic surface altering implements. An example of such an attempt is shown in U.S. Pat. No. 4,282,933, dated Aug. 11, 1981, to Takashi Suganami. This patent discloses, among other things, an automatic tilt control utilizing an inclinometer mounted on the dozer blade for sensing the tilt angle of the blade relative to the horizontal and a tilt angle setting device for selecting the desired tilt angle. The output from the inclinometer and the tilt angle setting device are compared and a corresponding signal is delivered to the tilt control system. This causes energization of a solenoid operated valve and tilting of the blade to the desired resultant angle. Tilting of the blade continues during operation to maintain the blade at the desired angle. Since inclinometers tend to be sensitive to motion and deliver erroneous signals when jostled about, the mounting of an inclinometer on a dozer blade, an implement that is constantly moved, vibrated, and subjected to the harshness of geographic surface altering operations is inappropriate.
Further, automatic control systems conceived for use on geographic surface altering machines have not proven satisfactory as they are inaccurate and tend to have a relatively short life caused by the harsh environment in which the geographic surface altering machine is operated.
Under the dynamics of vehicle operation, the tilt angle of the implement changes relative to the horizontal reference plane. This erratic movement affects the accuracy of the cut and fill operation and results in an irregular sloped surface. The use of an inclinometer, a generally static sensing device, on the machine frame does not solve this problem as it is not capable of dealing with the rate of change of implement tilt angle position caused by machine dynamics. No solution has been provided heretofore which addresses and corrects the tilt angle error caused by machine dynamics.
The present invention is directed to overcoming one or more of the problems as set forth above.